GB1282228A - Electronic circuit testing apparatus - Google Patents

Abstract

1282228 Testing logic circuits INTERNATIONAL BUSINESS MACHINES CORP 5 Feb 1970 [17 Feb 1969] 5557/70 Heading G1U A logic circuit 11, Fig.2b, which should produce an output signal which is either above both of two threshold levels Va', Vb', or below both levels, is tested by applying an appropriate input signal TC to it, and by applying the output signal TA from it to two threshold circuits 15a, 15b, arranged to produce either complementary binary signals on leads TB1, TB2, if the output signal TA is either above or below the range demarcated by the two threshold levels, or identical binary signals if the output signal lies between the threshold levels. The signals TB1, TB2 are applied to a logic circuit, as shown, which also receives gating signal G1 and G2 at times t4 and t5 respectively, and a signal TE indicative of the expected output signal from the logic unit under test, and which produces a result signal TR, from a latch 17. The operation of the complete circuit is summarized by the following table: The result signal TR is recorded at times t4 and t5 and correlated with the expected signal TE. A plurality of circuits are tested and the results evaluated under the control of a computer. A circuit employing known semi-conductor modules Fig.2a (not shown) is described for producing two-level signals for application to a circuit under test. The circuit incorporates a bi-stable circuit whose condition can be changed whenever a sync pulse is applied, and whose state determines the level of the output signal.